How do I activate my key on Steam?

1. Open the Steam client and sign in.
2. Click "Add a game" in the bottom-left corner → "Activate a Product on Steam".
3. Enter your key and confirm.
4. The game appears in your library — ready to install.

A key can be activated only once, on one account. Enter it without extra spaces and don't confuse 0/O and 1/I.